These can no be obtained by combining Unknown Seed with Truffle Mushroom.
Unknown Seed can be obtained with very low chance byproduct in Alchemy.

In EU Truffle Mushroom Hypha cost 18.7mil silver in Market Place.
Farming one in player fence will give in average of 62 Truffle Mushrooms (I harvested 10 Hyphas to get numbers).
Truffle Mushroom market value is 187k/pc, so Hypha cost about 100 mushrooms.

Manual gathering will be much easier and faster than wasting 10 grid farm fences for this farming, specially when Hypha cannot be breed.